In providing flow rate control to various types of dispensing systems, which are connected to either domestic or international water supplies, it is desired to provide a generally constant flow rate to the dispenser inlet despite being provided with wide variations in the water supply pressure. Various types of flow control devices have been employed for this purpose and a particular well-known device is a elastomeric flow washer which deforms resiliently under increasing supply pressure to restrict the flow orifice size thereby maintaining a constant flow rate. Such a device is illustrated in U.S. Pat. No. 2,816,572 issued to Pratt.
However, in providing flow control to the water inlet of the dispensing device, problems have been experienced in excessive noise where the restriction of the flow control device have produced cavitation. In cases where the flow control is applied at the inlet of an electrically operated water inlet valve, the noise problem has been particularly exacerbated by the flow cavitation causing resonant vibration of the surrounding valve body structure. This problem has been particularly troublesome in appliance water inlet valves having a body structure rigidly secured to a surrounding metal frame or cabinet of the dispenser.
Where the dispenser water inlet flow control device is required to control substantial restriction to accommodate relatively high water supply pressure for maintaining a constant flow rate to the device, severe high frequency vibration has been encountered as cavitation occurs at the flow control device and the resulting noise is perceived to be quite objectionable to the user. In this regard, efforts have been undertaken to inexpensively control the noise associated with the flow control devices employed for controlling the flow rate through such devices.
As is illustrated in U.S. Pat. No. 5,226,446 issued to Cooper, a flow noise reduction assembly is set forth having flow limiting orifice, that being an inlet pressure responsive flow control washer having flow limiting capabilities. Additionally, a conically faced diverter is disposed closely adjacent the down stream face of the orifice and an expansion chamber is disposed down stream of the flow diverter for noise attenuation. However, by providing the diverter down stream of the flow control washer, variations in fluid flow due to the diverter may continue to occur. Moreover, it is imperative that the diverter be sized in a manner which provides appropriate dispersion of the fluid flow without creating unnecessary turbulence in the flow of fluid through the system. In addition to the foregoing, the conically faced diverter disposed closely adjacent to down stream face of the orifice includes thin radial spokes which extend between the diverter and an outer rim thereof. Over time, these radial spokes may wear, thus requiring the assembly to be inspected and serviced on a regular basis.
As noted hereinabove, a typical water control valve is normally comprised of inlet and outlet orifices, diagrams for causing the opening and closing of the water flow path, an armature which drives a by-directional diaphragm and a coil structure which energizes and de-energizes the armature, thus resulting in the opening and closing of the water flow path. Other than the power consumption and physical space requirements of the valve, important requirements of the consumer were related to the consistency of the water flow, the noise level of the valve during its operating cycle and costs associated with maintaining the proper operation of the valve.
A valve of this type has a variety of uses. The most typical use of the types of valves set forth herein is to, upon command, initiate and maintain a water flow to fill a container to a predetermined quantity, after which the flow is stopped. Of utmost importance to the consumer is that the quantity of water supplied is at a particular rate and dispensed by a particular control scheme such that the total quantity of fluid dispensed would be within a desired tolerance. As noted hereinabove, due to the variability of the supply pressure, the flow rate of typical valves is not consistent over a range of for example 20 to 120 psig supply pressures. Accordingly, in that the customer is expecting a particular quantity or flow rate, a variation in the flow rate may ensue due to the inability of the valve to discern the supply pressure variation. In some instances, adjustment of the flow rate may be carried out manually, however, for most uses, automatic control is not only desirable, but required. One component of an automatic flow control device is a simple timer which is an inexpensive, accurate and even programmable method to obtain a desired result. Timers are generally accurate and repeatable over a long period of time, however, controlling the actual flow rate through the valve lends itself to unique dramatic considerations. Variations in basic pressure as well as time variable pressure must be handled in a manner which produces uniform flow rates over the life of the control valve.
Clearly, there is a need for a flow control valve which provides steady and constant fluid flow throughout a range of supply pressures as is often found in domestic and international water systems. Moreover, there is a need for a control valve which supplies substantially steady and constant flow through the valve while minimizing sound attenuation associated with prior art valves.